A. Technical Field
The present invention relates to a transponder for receiving a wireless electromagnetic query signal and for sending a wireless electromagnetic response signal with a first coil acting as an antenna for generating a first wired electrical incoming signal from the query signal and with at least one further coil acting as an antenna for generating a further wired electrical incoming signal from the query signal, and wherein an axis of the first coil and an axis of the further coil have different alignments in space.
The object of the present invention seeks to improve a transponder of this kind.
The object is achieved by a transponder as described in the introduction in such a way that the coils are assigned at least one means for limiting the voltage of the respective incoming signals, and wherein the incoming signals are routed via a first full-wave rectifier, respectively, in order to generate a rectified incoming signal, and wherein the rectified incoming signals are routed to a current-controlled source of current, respectively, for generating a current signal that corresponds to the respective incoming signal, and wherein the current signals are routed to a peak value of current detector, respectively, for generating a peak value of current signal, and wherein the peak value of current signals are routed to a comparison arrangement for comparing the generated peak value of current signals, and wherein the comparison arrangement is configured for generating a control signal that indicates the strongest peak value of current signal of the generated peak value of current signals.
B. Background of the Invention
A transponder is understood to mean a transmission and receiving means that transmits, upon receiving a wireless electromagnetic query signal, a wireless electromagnetic response signal. The query signal therein is generated by a query device that is especially configured for this purpose and that is typically also configured to receive the response signal. Such combinations of transponders and query devices can be used, in particular, for purposes of keyless access control and/or keyless use control in motor vehicles.
Coils, in particular cylinder-shaped coils, can generally be used as antennas for receiving wireless electromagnetic signals, and wherein they essentially respond to the magnetic component of the field converting it to a wired electrical signal. However, therein they demonstrate a pronounced directional effect. If the axis of the coil is directed to the transmitter, there results an incoming minimum, if it is perpendicular in relation to the direction of the transmitter there results, on the other hand, an incoming maximum.